A bipartisan group of eight senators working to draft legislation to change immigration policy continues to move forward and is expected to unveil a bill as soon as the second week of April, Senate Democratic aides said.

“The progress has been steady,” said one senior Senate Democratic aide with knowledge of the negotiations.

The group had planned to release its package before the end of March, but the unveiling will likely slip until after the upcoming recess, which includes the last week of March and first week of April.

“We’re still on schedule,” the aide said, but the group doesn’t want to release the measure during recess.

“We think we are still able to have an agreement in [late] March, but the work period puts the unveil in April,” the aide added.

Another senior Senate Democratic aide familiar with the talks said the group would likely be very close to being done by the end of March.

However, many aspects of the package remain to be negotiated, aides said.

“There are a lot of blanks to be filled in,” the Democratic aide said.

For example, the group must agree on what measure to use to determine that the border is sufficiently secure. Once the borders are secured, 11 million illegal immigrants in the United States would be able to begin to apply for citizenship, which will be a long path contingent on other criteria including learning English and paying fines.

Other specifics that need to be worked out include how much of a fine illegal immigrants would have to pay, how the government would determine how much in back taxes they should pay and the overall length of time the process of becoming a citizen should take.

Along with a path to citizenship, the framework for the Senate bill, which was released in January, includes overhauling the existing immigration system, reducing the hiring of undocumented workers and creating a guest worker program.

The group is doing its best to guard details of the negotiations from leaking out because it want to release the package as a unit.

“All these aspects [of the bill] are interrelated,” one aide said, adding that the senators want to “roll it out at once.”

The aide used an adage often invoked by lawmakers during sensitive talks on far-reaching, high-profile legislation.

“The spirit of negotiations [is] very much that nothing is agreed to until everything is agreed to,” the aide said.

However, The Los Angeles Times reported Monday that group had agreed on how to offer legal status to the 11 million illegal immigrants already in the United States. The reported legislative language tracks closely with the principles outlined by the group.

The Senate group includes Democrats Charles E. Schumer of New York, Richard J. Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado and Republicans John McCain of Arizona, Lindsey Graham of South Carolina, Marco Rubio of Florida and Jeff Flake of Arizona.

A bipartisan group in the House is also working on legislation, but the package it is crafting is likely to be somewhat different from the Senate version.

Rep. Luis V. Gutierrez, D-Ill., a member of the House group, said Sunday on Telemundo’s “Enfoque” that he expects both bills to be unveiled soon.

“I think — though I am not speaking for any group — given what I have heard ... that you could soon see a plan from the Senate and a plan from the House. They will not be identical; they will be different from one another,” Gutierrez said.

He said that there might be things in the House bill that will cause heartburn on the left and the right “but we have to find 218 votes.”

Gutierrez said he thinks the House bill could include a path to citizenship that puts a stop to the deportation of illegal immigrants, preserves worker’s rights, provides the right to travel, and ultimately, the right to keep a family together.

“These things, we think, can be achieved” in legislation, he said.

House Majority Whip Kevin McCarthy, R-Calif., agreed that the Senate bill may not be the only game in town.

“I wouldn’t underestimate the House’s ability to pass the immigration bill,” McCarthy said Sunday on CNN’s “State of the Union.” “I think we have plenty ideas on that, and I think there’s an opportunity that we can move the ball as well.”